In general, a method for manufacturing a substrate, to which a semiconductor die, solder balls, and the like are electrically connected, includes an insulation layer provision step of providing an insulation layer having metallic foil formed on both surfaces thereof. A number of holes are formed on both surfaces of the insulation layer. A primary plating step is done by forming an electroless plating and an electrolytic plating on the inner wall of the holes and on the surface of the metallic foil so that the metallic foil on both surfaces of the insulation layer is electrically connected to each other via the holes. A patterning step is performed by attaching dry film to the platings and forming actual circuit patterns through exposure/development/etching processes. A solder mask is formed by printing a solder mask and exposing a region, to which a semiconductor die, solder balls, and the like are to be actually connected, while covering remaining regions, through exposure/development processes. A secondary plating step is done by forming nickel/gold platings in a predetermined region of the circuit patterns exposed by the solder mask.
In the case of a conventional substrate, a bus line is formed on the outer periphery of the substrate in the patterning step in such a manner that the bus line is thicker or larger than the circuit patterns. In addition, a number of lead-in lines are formed on the bus line to connect all circuit patterns to one another. Such formation of the bus line and lead-in lines is for the purpose of forming nickel/gold platings in a predetermined region of the circuit patterns, which has been exposed by the solder mask in the second plating step, with a sufficient thickness in an electrolytic plating method. Without the bus line and lead-in lines, the nickel/gold platings cannot be formed in an electrolytic plating method, but in an electroless plating method. If the electroless plating method is used, it is difficult to obtain sufficient reliability at a package level in terms of wire bonding and solder weldability. The bus line is removed through a sewing process after the nickel/gold platings are formed, and all circuit patterns are electrically independent in the end. However, the lead-in lines remain connected to the circuit patterns and cause a number of problems when designing a substrate or operating a semiconductor device.
First, formation of lead-in lines from all circuit patterns towards the outer periphery of the substrate decreases the density of the circuit patterns. Particularly, lead-in lines are formed in positions, where circuit patterns are supposed to be formed, and fewer circuit patterns are allowed to be formed. In addition, the lead-in lines decrease the degree of freedom in designing the circuit patterns and render the design of circuit patterns very difficult.
Second, a large number of lead-in lines left on the insulation layer, even after the substrate is manufactured, reflect and delay electric signals flowing through the circuit patterns. As such, the lead-in lines substantially degrade the electrical performance of the semiconductor device.
Third, a large number of lead-in lines exposed to the outside via the edge of the substrate are likely to contact an external conductor while the semiconductor device is transported or handled. Particularly, the lead-in lines may cause static electricity to flow into the semiconductor device or generate an unnecessary short circuit. This may damage the semiconductor device.
In order to solve these problems, a substrate having no bus line and lead-in line has been developed and studied. However, conventional methods for manufacturing a substrate without bus line and lead-line have a problem in that, in order to form nickel/gold platings, separate processes for dry film attachment, exposure, and etching must be performed a number of times. Particularly, the dry film process, which must be repeated a number of times to form nickel/gold platings, increases the manufacturing cost of the substrate and decreases the yield rate thereof.
Therefore, a need existed to provide a device and method to overcome the above problem.